The present invention relates to microelectronic assemblies and, more particularly, to surface treatment of microelectronic device substrate for underfill and mold compound adhesion.
In the following description, reference is made to microelectronic die, carrier substrate, microelectronic device, and microelectronic package. A microelectronic die comprises a die substrate upon which microcircuits are formed. A microelectronic device is defined as a microelectronic die electrically interconnected with a carrier substrate. A carrier substrate is a structure comprising conductive pathways through which microcircuits of the microelectronic die communicate with external components. A microelectronic package is defined as a microelectronic device that is assembled into a finished package with additional components, such as electrical interconnects, die underfill, a die lid, and a heat dissipation device, among others. An example of a microelectronic package includes, but is not limited to, a flip-chip ball grid array (FC-BGA) microprocessor package.
During the packaging of the microelectronic device into a microelectronic package, underfill material is provided and cured within the space between the microelectronic die and the carrier substrate and surrounding the interconnects. The process of applying underfill to the space between the components is well known. Commonly the underfill material is drawn into the space between the components by capillary action filling the space and surrounding the interconnects with no voids and forming a fillet around the perimeter of the microelectronic die. The underfill material helps to prevent loading on the interconnects during thermal cycling by supporting the components.
In an effort to increase the efficiency of the production of microelectronic devices, efforts have been made to produce many devices simultaneously rather than one at a time. The process is known as Molded Matrix Array Packaging (MMAP). MMAP technology provides a low cost method of simultaneously packaging a plurality of microelectronic dice in a minimal number of process steps.
Using chip-scale flip-chip package technology as an example, MMAP allows multiple dice of the same configuration to be interconnected onto a single carrier substrate panel in an ordered array, underfilled, encapsulated with mold compound, and singulated into individual microelectronic devices by cutting the carrier substrate panel in the area between each microelectronic die, known as the inter-die region. The MMAP process significantly reduces handling as the process steps are performed simultaneously on every microelectronic die.
A critical step in MMAP technology is the adhesion of mold compound to the substrate in the inter-die areas. This is because the final microelectronic device dimension is very close to that possessed by the microelectronic die. Consequently, the bonding area of the mold compound to carrier substrate panel is very small and could possibly compromise package integrity if this bond joint does not possess sufficient bond strength. It has been well established in MMAP molding that the inter-die area must be free of underfill material in order to achieve optimal mold compound to carrier substrate panel adhesion. This is critical because low adhesion will cause delamination at the mold compound/underfill interface upon singulation.
Methods have been attempted to address the issue of maintaining the inter-die areas free of underfill material for MMAP substrates that are underfilled with capillary or no-flow underfill material. Some of those methods include: decreasing carrier substrate panel die density, thus increasing inter-die distance; using substrate dams; closely controlling dispensing volume; and employing complicated and slow dispensing programs. Generally, such methods have been found to be undesirable due to cost, low through-put, and undesirable substrate matrix die densities.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a significant need in the art for methods that address the problem of maintaining the inter-die areas free of underfill material for MMAP.